Sudden cardiac death and the use of implantable cardioverter-defibrillators in pediatric patients

Background. During the past decade, the implantable cardioverter-defibrillator (ICD) has emerged as the primary therapeutic option for survivors of sudden cardiac death (SCD). Investigation of the clinical efficacy of these devices has primarily assessed outcome in adults with coronary artery disease. The purpose of this cooperative, international study was to evaluate the impact of ICDs on the pediatric population of SCD survivors, based on an analysis of the clinical characteristics and outcomes of young patients who underwent ICD implantation following an episode of life-threatening ventricular tachycardia or resuscitation from SCD. Methods and Results. An initial data base, established by contacting the manufacturers of the various commercially and investigationally available devices, identified 177 patients who were less than 20 years of age at the time of initial implantation of an ICD. With this data base as a reference, detailed responses were subsequently obtained from physicians involved in the care of 125 (71%) of these patients. The patients ranged in age from 1.9 to 19.9 years (mean, 14.5±4 years) and weighed 9.7-117 kg (mean, 44.6±14 kg). Of the 125 patients, 76% were survivors of SCD, 10% had drug refractory ventricular tachycardia, and 10% had syncope with heart disease and inducible sustained ventricular tachyarrhythmias. The most common types of associated cardiovascular disease were hypertrophic and dilated cardiomyopathies (54%), primary electrical diseases (26%), and congenital heart defects (18%). Ventricular function was abnormal in 46% of the patients. During a mean follow-up of 31±23 months, at least one ICD discharge occurred in 85 of the 125 (68%) patients. Seventy-three patients (59%) received at least one appropriate ICD discharge, and 25 patients (20%) had one or more spurious or indeterminate discharges. Duration of follow-up >24 months (p=0.001) and inducibility of a sustained ventricular arrhythmia (p=0.05) were correlated with appropriate ICD discharges. There were nine deaths during the study period: five sudden, two due to recurrent ventricular arrhythmias, and two related to congestive heart failure. Abnormal ventricular function (p=0.002) and prior ICD discharge (p=0.01) were univariate correlates of patient mortality; by multivariate logistic regression, abnormal ventricular function was the only significant correlate of death (p=0.005). By actuarial analysis, the estimated overall post-ICD implant survival rates at 1, 2, and 5 years were 95%, 93%, and 85%, respectively. The corresponding sudden death-free survival rates were 97%, 95%, and 90%. Conclusions. Pediatric patients resuscitated from SCD appear to remain at risk for recurrence of life-threatening tachyarrhythmias. During a mean follow-up of 31 months, the ICD provided an effective therapy for such arrhythmias in the majority of patients in this study. Following ICD implant, impaired ventricular function was the primary factor correlated with mortality. The patterns of ICD discharge observed in young patients and, thus, inferred risk of recurrent life threatening arrhythmias are similar to those of adult survivors of SCD. Thus, the use of ICDs in pediatric patients, with implant selection criteria similar to adults, appears valid.